Hot water rotary drum blanchers have long been used in the food processing industry to blanch or cook a continuous throughput of food product such as pasta, green peas, corn, beans and other processed food and vegetables. Uniformity and product integrity are paramount concerns in preparing food for human consumption. To advance the food product through the blancher in a gentle and non-destructive manner, helical augers mounted within a water filled tank have long been used. The auger is mounted within a cylindrical drum having a perforated steel screen skin which allows water in the tank to flow freely into the interior of the drum. Rotation of the drum gently advances food product from the tank inlet end to the tank discharge end.
At one time, these augers were mounted on a central drive shaft and were driven directly by an engaged sprocket and motor. A central drive shaft, however, presented several problems. First, the extension of the drive shaft axially through the inlet end of the tank interfered with the introduction of food product into the cylindrical drum. Furthermore, food product coming into contact with the central shaft was subject to damage. In addition, experience showed that central drive shafts were prone to breakage.
Conventional blanchers have eliminated the breakage problem of the central drive shaft by mounting the helical auger flights on a central cylindrical core which extends through the inlet and outlet ends of the blancher tank to define cylindrical journals which are supported on two rotatable trunnions at each end. The cylindrical core is of sufficient diameter to allow the introduction of an infeed chute through the inlet journal. To allow the food product to pass into and exit from the cylindrical drum, the core does not completely extend to the inlet and outlet ends of the blancher tank. Rather, a number of symmetrically spaced straight steel bars that are spaced a distance from the rotational axis of the drum equal to the radius of the core extend from each end of the core respectively to the inlet end and the outlet end. While the construction and arrangement of the bars and the core are sufficiently structurally rigid and do not interfere with the product introduction through the infeed chute, at the inlet end, the bars continually pass through the path of infed product during rotation of the bars, the core and the auger flights. As a result, the rotating bars can come into contact with infed food product and can damage product, if it is at all delicate.
This is because the bars extend from the end of the core parallel to the axis of rotation of the drum toward the inlet end and are spaced outwardly from the radius the same distance as the radius of the core. As a result of this construction, infed food product can be contacted by one or more rotating bars very shortly upon entering the water. Since this contact can occur shortly after entering the water, infed product can relatively severely impact against a bar increasing the likelihood that it will be damaged. Moreover, these bars are of relatively small cross section which further increases the likelihood of damaging product because no significant layer of cushioning water can build up along the leading edge of each bar while it is immersed in the water.
If the product is in pouches, these bars impacting against the pouches can burst pouches, undesirably causing solids to be dispersed within the drum and tank. If solids are dispersed within the water in the tank, it can require undesirable and costly environmental treatment before the tank water can be disposed. This type of prior art cored blancher construction is further disclosed and shown in FIG. 1 of U.S. Pat. No. 5,146,841.
Additionally, the construction and arrangement of the bars and auger core of these prior art blanchers have traditionally limited the size of the inlet opening to less than or about equal to the diameter of the auger core because the bars are attached to the end of the core and extend parallel to the drum axis of rotation. This construction also undesirably limits the amount of food product that can be infed into the drum at one time.
A commercially successful blancher that solves this problem is disclosed in the aforementioned '841 patent, which is assigned to the assignee herein. To enable the diameter of the inlet opening to be increased to a size larger than the diameter of the auger core, the end of the core does not extend to the inlet opening and is not connected to the inlet end of the drum by bars. The blancher drum of the '841 patent has support channels of generally C-shaped cross section that extend axially from the inlet plate to the outlet plate of the drum to help provide sufficient structural rigidity to the drum, helical augers, and core enabling the connecting bars between the core and inlet end of the drum to be eliminated. While this blancher drum construction has proven to be extremely commercially successful for blanchers having an axial length of up to about twenty four feet and a drum diameter of about seventy-two inches, there exists a desire to improve upon the structural rigidity of blanchers having a larger diameter and/or a longer axial length.
What is needed is a rotating blancher drum which has improved structural rigidity while providing minimal obstruction to food product being infed into the drum through the inlet. What is also needed is a drum possessing the requisite structural rigidity for producing a blancher having a relatively long length and/or large diameter. What is still further needed is an improved assembly for securing the core and/or auger to the inlet end plate of the drum to provide the desired structural rigidity to the drum while also minimizing and preferably substantially preventing destruction of food product entering the drum.